wouters



REGULATOR FOR CALUTRON ION SOURCE Filed Jan. 21, 1948 I5 Sheets-Sheet 1m I\ 2 Q x ux Q w: it w m m 28: (t8: QEQ mks: INVENTOR. h 9 a lg Lows FhOUrERJ m5 BY ATTORNEY.

Jan. 31, 1956 F. WOUTERS 2,733,342

REGULATOR FOR CALUTRON ION SOURCE Filed Jan. 21. 1948 3 Sheets-Sheet 2 aww M R: Y 6L 5 EN Q w 3-- No I 2 & IW%A WK W M L 2 4/ /O Y PlIilllPJ K m7 T J a M Z 3 4 4 4 4 A++ a a R w r 0...? MM aw er m Y ma may MW a mm mm5 mm mm Mm mm AP P P P CP AP LP P A A ML 5 Au Au M u w mw w wm mmw F NWJ www mm; M A E 3 Sheets-Sheet 5 INVENTOR. LOU/J F 14/007525 L. F.WOUTERS ATTORNEY.

REGULATOR FOR CALUTRON ION SOURCE Jan. 31, 1956 Filed Jan. 21, 19482,733,342 REGULATOR FOR CALUTRON ION SOURCE Louis F. Wouters, Oakland,Calif., assignor to the United States of America as represented by theUnited States Atomic Energy Commission Application January 21, 1948,Serial No. 3,587

12 Claims. (Cl. 250-419) The present invention relates to regulators forelectric discharge devices and more particularly to regulators forcalutron ion sources.

It is an object of this invention to provide a regulator for stabilizingthe operation of a calutron ion generator.

Another object of this invention is to provide a regulator forstabilizing the operation of a calutron ion gen erator of the arcdischarge type.

Still another object of this invention is to provide a regulator for acalutron ion generator of the hot cathode arc discharge type which has ahighly stable rate of ion production.

At the outset it is noted that a calutron is a machine of the characterdisclosed in the copending application of Ernest 0. Lawrence, Serial No.557,784, filed October 9, 1944, now Patent Number 2,709,222, issued May24,

1955. A calutron, as therein described, and is employed to separate theconstituent isotopes of an element and more particularly to'increase theproportion of a selected isotope in an element containing severalisotopes in order to produce the element enriched with the selectedisotope. For example, the machine is especially useful in producinguranium enriched with U Such a calutron essentially comprises means forvaporizing a quantity of material containing an element that is to beenriched with a selected one of its several isotopes; means forsubjecting the vapor to ionization, whereby at least a portion of thevapor is ionized causing ions of the several isotopes of the element tobe produced; electrical means for segregating the ions from theunionized vapor and for accelerating the segregated ions throughrelatively high velocities; electromagnetic means for deflecting theions along curved paths, the radii of curvatures of the paths of theions being proportional to the square roots of the masses of the ions,whereby the ions are concentrated in accordance with their masses; andmeans for de-ionizing and collecting the ions of the selected ions thusconcentrated thereby to produce a deposit of the element enriched withthe selected isotope.

The invention, both as to its organization and method of operationtogether with other objects and advantages thereof, will best beunderstood by reference to the following specification taken inconnection with the accompanying drawings, in which:

Figure 1 is a diagrammatic view of a calutron and the various currentsupplies and arc regulator connected to the ion generator thereof; 7

Fig. 2 is a diagrammatic sectional view of the calutron taken along theline 22 of Fig. 1;

Fig. 3 is a diagrammatic view of a calutron ion generator together withthe various current supplies associated therewith and a modified form ofarc regulator connected thereto; Fig. 4 is a diagrammatic view of acalutron ion genererator together with the various current suppliesassociated therewith and another modified form of arc regulatorconnected thereto; and

Fig. 5 is a diagrammatic view of a calutron ion gen- 2,733,342 C6iatented Jan. 31, 1956 erator together with the various current suppliesassociated therewith and still another modified form of arc regulatorconnected thereto.

Referring now more particularly to Figs. 1 and 2 of the drawings, thereis illustrated a representative example of a calutron 10 of thecharacter noted, that comprises magnetic field structure including upperand lower pole pieces 11 and 12, provided with substantially flatparallel spaced-apart pole faces, and a tank 13 disposed between thepole faces of the pole pieces 11 and 12. The pole pieces 11 and 12 carrywindings, not shown, which are adapted to be energized in order toproduce a substantially uniform and relatively strong magnetic fieldtherebetween, which magnetic field passes through the tank 13 and thevarious parts housed therein. The tank 13 is of tubular configuration,being substantially crescent-shaped in plan, and comprisingsubstantially flat parallel spaced-apart top and bottom walls 14 and 15,upstanding curved inner and outer side walls 16 and 17, and end walls 18and 19. The end walls 18 and 19 close the opposite ends of the tubulartank 13 and are adapted to be removably secured in place, whereby thetank 13 is hermetically sealed. Also, vacuum pumping apparatus, notshown, is associated with the tank 13, whereby the interior of the tank13 may be evacuated to a pressure of the order of 10- to 10- mm. Hg.Preferably, the component parts of the tank 13 are formed of steel, thetop and bottom walls 14 and 15 thereof being spaced a short distancefrom the pole faces of the upper and lower pole pieces 11 and 12,respectively, the tank 13 being retained in such position in anysuitable manner, whereby the top and bottom walls 14 and 15 constitutein effect pole pieces with respect to the interior of the tank "13, asexplained more fully hereinafter.

The removable end wall 18 suitably supports a source unit 20 comprisinga charge receptacle 21 and a communicating arc block 22. An electricheater 23 is arranged in heat exchange relation with the chargereceptacle 21 and is adapted to be connected to a suitable source ofheater supply 41, whereby the charge receptacle 21 may be appropriatelyheated, the charge receptacle 21 being formed of steel or the like. Theare block 22 is formed, at least partially, of carbon or graphite and issubstantially C-shaped in plan, an upstanding slot 24 being formed inthe wall thereof remote from the charge receptacle 21. Thus, the arcblock 22 is of hollow construction, the cavity therein communicatingwith the interior of the charge receptacle 21.

Also, the removable end wall 18 carries a filamentary cathode 25 adaptedto be connected to a suitable source of filament supply 42, thefilamentary cathode 25 overhanging but spaced apart from the upper endof the arc block 22 and arranged in alignment with respect to the upperend of the cavity formed therein. The are block 22 carries an anode 26disposed adjacent the lower end thereof and arranged in alignment withrespect to the cavity formed therein. Also, the arc block 22 carries acollimating electrode 27 disposed adjacent the upper end thereof andhaving an elongated collimating slot 28 formed therethrough and arrangedin alignment with respect to the filamentary cathode 25 as well as theanode 26 and the cavity formed in the arc block 22. In addition, abombardment cathode 37 and a control electrode 35 also having anelongated slot 36 formed therethrough are interposed between thefilamentary cathode 25 and the collimating electrode 27 and arranged inalignment therebetween, the control electrode 35 being adjacent thefilamentary cathode 25. Thus, it will be understood that the are systemincludes a combination of structure arranged in mutual alignment anddisposed in the following sequence: filamentary cathode 25, controlelectrode 35, bombardment cathode 37, collimating electrode 27, areblock cavity and anode 26. Both the anode 26 and the collimatingelectrode 27 are electrically connected to the source unit 29 which inturn is grounded; likewise, the tank 13 is grounded. The bombardmentcathode 37 and the cooperating. anode 26 are adapted to be connected toa suitable source of are supply 43. Also, a suitable bombardment voltagesupply 44 is adapted to be connected between the bombardment cathode 37and the filamentary cathode 25, the positive and negative terminals ofthis supply being respectively connected to the bombardment cathode 37and the filamentary cathode 25. The control electrode 35 is adapted tobe connected to a suitable arc regulator 46 whereby the electronemission from the filamentary cathode 25 to the bombardment cathode 37may be controlled. It should be noted that the above-described electrodearrangement is disclosed in the copending application of Louis F.Wouters, Serial No. 528,818, filed March 31, 1944.

Further, the removable end wall 18 carries ion accelerating structure 39formed of carbon or graphite and disposed in spaced-apart relation withrespect to the wall of the arc block 22 in which the slot 24 is formed.More specifically, a slit 40 is formed in the ion accelerating structure39 and arranged in substantial alignment with respect to the slot 24formed in the wall of the arc block 22. A suitable source ofaccelerating electrode supply 45 is adapted to be connected between thearc block 22 and the ion accelerating structure 39, the positive andnegative terminals of the supply mentioned being respectively connectedto the arc block 22 and to the ion accelerating structure 39. Further,the positive terminal of the ion accelerating potential is grounded.

The removable end wall 19 suitably supports a collector block 29 formedof stainless steel or the like and provided with two laterallyspaced-apart cavities or pockets 30 and 31 which respectivelycommunicate with aligned slots 32 and 33 formed in the wall of thecollector block 29 disposed remote from the removable end wall 19. It isnoted that the pockets 30 and 31 are adapted to receive two constituentisotopes of an element which have been separated in the calutron 10, asexplained more fully hereinafter.

Further, the inner Wall 16 suitably supports a tubular liner 34 formedof copper or the like, rectangular in vertical cross-section, disposedwithin the tank 13 and spaced from the walls 14, 15, 16 and 17. One endof the tubular liner 34 terminates adjacent the accelerating structure39; and the other end of the tubular liner 34 terminates adjacent thecollector block 29; the tubular liner 34' constituting an electrostaticshield for the high velocity ions traversing the curved paths betweenthe slit 40 formed in the ion accelerating structure 39 and the slots 32and 33 formed in the collector block 29, as explained more fullyhereinafter. Finally, the tubular liner 34 is electrically connected tothe ion accelerating structure 39 and to the collector block 29. Thus,it will be understood that the source unit 20 and the tank 13areconnected to the positive grounded terminal of the acceleratingelectrode supply; while the ion accelerating structure 39, the tubularliner 34 and the collector block 29 are connected to the ungroundednegative terminal of the accelerating electrode supply; the ionaccelerating structure 39, the tubular liner 34 and the collector block29 being electrically insulated from the component parts of the tank 13.

Considering now the general principle of operation of the calutron 10, acharge comprising a compound of the element to be treated is placed inthe charge receptacle 21, the compound of the element mentioned beingone which may be readily vaporized. The end. walls 18 and 19 aresecurely attached to theopen ends of the tank 13, whereby the tank 13is. hermetically'sealed. The various electrical connections arecompleted and opera tion of the vacuum pumping apparatus, not shown,associated with the tank 13 is initiated. When a pressure of the orderof 10- to 10 mm. Hg is established within the tank 13, the electriccircuits for the windings, not shown, associated with the pole pieces 11and 12 are closed and adjusted, whereby a predetermined magnetic fieldis establishes therebetween traversing the tank 13. The electric circuitfor the heater 23 is closed, whereby the charge in the charge receptacle21 is heated and vaporized. The vapor fills the charge receptacle 21 andis conducted into the communicating cavity formed in the arc block 22.The electric circuit for the filamentary cathode 25 is closed, wherebythe filamentary cathode is heated and rendered electron emissive. Nextthe bombardment voltage circuit and the are regulator circuit arecompleted, whereupon electrons from the filamentary cathode 25 areaccelerated through the elongated opening 36 in the control electrode 35and impinge upon the bombardment cathode 37, rendering it electronemissive by bombardment heating. Then the electric circuit between thebombardment cathode 37 and the anode 26 is closed, whereby an arcdischarge is struck therebetween, electrons proceeding from thebombardment cathode 37 through the collimating slot 23 formed in thecollimating electrode 27 to the anode 26. The collimating slot 28 formedin the collimating electrode 27 defines the cross-section of the streamof electrons proceeding into the arc block 22, whereby the are dischargehas a ribbon-like configuration and breaks up the molecular form of thecompound of the vapor to a considerable extent, producing positive ionsof the element that is to be enriched with the selected one of itsisotopes. A more detailed explanation of the operation of the aforesaidarrangement may be had by referring to the copending application ofLouis F. Wouters, Serial No. 528,818, filed March 31, 1944, now PatentNo. 2,717,962.

The electric circuit between the arc block 22 and the ion acceleratingstructure 39 is completed, the ion accelerating structure 39 being at ahigh negative potential with respect to the arc block 22, wherebypositive ions in the arc block 22 are attracted by the ionacceleratingstructure 39 and accelerated through the voltage impressedtherebetween. More particularly, the positive ions proceed from thecavity formed in the arc block 22 through the slot 24 formed in the Wallthereof, and across the space between the ion accelerating structure 39and the adjacent wall of the arc block 22, and thence through the slit40 formed in the ion accelerating struc ture 39 into the interior of thetubular liner 34. The high-velocity positive ions form a verticalupstanding ribbon or beam proceeding from the cavity formed in the arcblock- 22 through the slot 24 and the aligned slit 40 into the tubularliner 34.

As previously noted, the collector block 29, as well as the tubularliner 34, is electrically connected to the ion accelerating structure39, whereby there is an electric-field-free path for the high-velocitypositive ions disposed between the ion accelerating structure 39 and thecollector block 29 within the tubular liner 34. The highvelocitypositive ions entering the adjacent end of the liner 34 are deflectedfrom their normal. straight-line path and from a vertical plane passing.through the slot 24 and the aligned slit 40, due to the effect of. therelatively strong magnetic field maintained through the space within thetank 13 and the liner 34 through which the positive ions travel, wherebythe positive ions describe arcs, the radii of which are proportional tothe square roots ofthe masses of the ions and consequently of theisotopes of the element mentioned. Thus, ions of the relatively lightisotopes of the element describe an interior arc of relatively shortradius and are focused through the slot 32 into the pocket 30 formed inthe collector block 29; Whereas ions-v ofthe relatively heavy isotopeofthe element describe an exterior arc of relatively long radius and arefocused through the slot- 33 into thepocket- 31 formed in the collectorblock 29. Ac-

cordingly, the relatively light ions are collected in the pocket 30 andare de-ionized to produce a deposit of the relatively light isotope ofthe element therein; while the relatively heavy ions are collected inthe pocket 31 and are de-ionized to produce a deposit of the relativelyheavy isotope of the element therein. a

After all of the charge in the charge receptacle 21 has been vaporized,all of the electric circuits are interrupted and the end wall 18 isremoved so that another charge may be placed in the charge receptacle 21and subsequently vaporized in the manner explained above. After asuitable number of charges have been vaporized in order to obtainappropriate deposits of the isotopes of the element in the pockets 30and 31 of the collector block 29, the end wall 19 may be removed and thedeposits of the collected isotopes of the pockets 30 and 31 in thecollector block 29 may be reclaimed.

Of course, it will be understood that the various dimensions of theparts of the calutron 10, the various electrical potentials appliedbetween the various electrical parts thereof, as well as the strength ofthe magnetic field between the pole pieces 11 and 12, are suitablycorrelated with respect to each other, depending upon the mass numbersof the several isotopes of the element which is to be treated therein.In this connection reference is again made to the copending applicationof Ernest 0. Lawrence, for a complete specification of a calutronespecially designed for the production of uranium enriched with theisotope U By way of illustration, it is noted that when the calutron isemployed in order to produce uranium enriched with U the compound ofuranium which is suggested as a suitable charge in the charge receptacle21 is U014, as this compound may be readily vaporized and the molecularform of the vapor may be readily broken up to form positive ions ofuranium with great facility. In this case, uranium enriched with U iscollected in the pocket 30 of the collector block 29, and uraniumcomprising principally U is collected in the pocket 31 of the collectorblock 29. Also, it is noted that from a practical standpoint, thedeposit of uranium collected in the pocket 30 of the collector block 29contains considerable amounts of U in view of the fact that this isotopecomprises the dominant constituent of normal uranium. Furthermore, thedeposit of uranium collected in the pocket 30 of the collector block 29contains a considerably increased amount of U in view of the fact thatit is not ordinarily feasible to separate U and U in the production ofrelatively large quantities of uranium enriched with U for commercialpurposes. Accordingly, in this example the uranium deposited in thepocket 30 of the collector block 29 is considerably enriched,'both withU and with U and considerably impoverished with respect to U as comparedto natural or normal uranium.

In the operation of the calutron 10, it is highly desirable that arelatively intense stable beam of positive ions be projected by the ionaccelerating structure 39 through the liner 34 toward the collectorblock 29 which operating condition requires that the source unitpresents to the accelerating structure 39 a high density plasma surfacewhich is extremely stable in shape, position and ion density. As hasbeen heretofore described, in order to obtain such a plasma surface therate of ion production by the arc discharging in the source unit 20 mustbe substantially constant. This has been accomplished by controlling theheating energy applied to the arc cathode 37 inversely as the arccurrent, by means of an arc regulator.

Considering now in more particular the electrical connections of thecalutron ion generator. and associated. arc regulator .of Figs. 1 and 2,the filament supply 42 furnishes power to the filamentary cathodethrough busbars 5 3 and 54, busbar 54 beingv also connected to the minusterminal of the bombardment voltage supply 44 and to potentiometer 51and resistor through terminals B and F, respectively, of the controlnetwork 46. The other end of the potentiometer 51 connects to the anodeof vacuum tube 49 and to the positive terminal of the bombardmentvoltage supply 44, this positive terminal also connecting to thebombardment cathode 37 of the ion generator. The other end of resistor50 is connected to the cathode and the control grid of vacuum tube 49and also through terminal G to the control electrode 35 of the iongenerator. The positive terminals of the are supply 43 and theaccelerating electrode supply 45 connect to the arc block 22 and toground, the negative terminal of the latter supply being connected tothe accelerating electrode 39. The negative terminal of arc supply 43connects to the bombardment cathode 37 of the ion generator viaterminals K and J, these terminals being connected to solenoid 47 whichis oriented to give a magnetic field parallel to the axis of vacuum tube49. Variable resistor 48 is connected across solenoid 47 for the purposeof varying the proportion of the are current flowing therethrough, andthus serves as the arc current control. Screen grid potential of vacuumtube 49 is supplied from the variable contact of potentiometer 51,through the current limiting resistor 52. Terminals H and I areconnected to a suitable source of filament voltage.

The electrical connections of the ion generator and are regulator havingbeen described, the detailed operation will now be considered. Assumingthat the various associated supplies have been energized and filamentarycathode 25 heated to emissive temperature, current from the negativeterminal of the bombardment voltage supply 44 flows to filamentarycathode 25 and thence by electron emission through the elongated opening36 in the control electrode 35 to the bombardment cathode 37, heating itto thermionic emissive temperature by bombardment. From the bombardmentcathode 37, the current returns to the positive terminal of the bombardment voltage supply 44. It is noted that a portion of the emissioncurrent from the filamentary cathode 25 may flow to the grid controlelectrode 35 and return to the positive terminal of the bombardmentvoltage supply-through vacuum tube 49. Current from the negativeterminal of the are supply 43 flows through the parallel combination ofthe solenoid 47 and variable resistor 48 to the bombardment cathode, andthence by electron emission through the arc discharge to the anode 26and back to the positive terminal of the arc supply 43. The vacuum tube49 and resistor 50 comprise a voltage divider supplying the potential tothe control electrode 35, and the resistance of vacuum tube 49 beingcontrolled by the arc current flowing through solenoid 47. Thus, if thearc current tends to increase, the increased magnetic field fromsolenoid 47 will increase the resistance of vacuum tube 49, therebyreducing the potential drop across resistor 50 and hence the positivegrid potential supplied to control electrode 35. This results in areduction of bombardment current to the bombardment cathode 37,decreasing its electron emission and causing a reduction of arc currentthat opposes the original increase. In this manner the arc current isstabilized.

Referring now to Figs. 3, 4, and 5, it is observed that the modified arcregulators illustrated therein are connected to the calutron iongenerator and associated supplies in a manner similar to that of theunmodified regulator circuit described above and illustrated in Fig. 1.However, inasmuch as the methods used to obtain a signal from the arccurrent and the means of developing a control electrode potential aredifferent therefrom, a short description of each modification will begiven. It is noted that these modified circuits are adapted to work witha control electrode that is biased negatively with respect to thefilamentary cathode.

In Fig. 3 the modified regulator 46a is associated with the arc currentcircuit by means of terminals J and K,

terminal I being connected to the bombardment cathode 1 37 and terminalK being connected to the negative terminal ofthe arc supply 43. Thecontrol potentialdeveloped by the regulator is impressed upon the iongenerator control electrode via terminals B and- G, terminal Bbeingconnected to the filamentbusbar' 54 and to the negative terminal ofthe bombardment voltage supply 44 and terminal G being connected to thecontrol electrode 35. Transformers 56 and 60, energized from a suitablesource of A. C. power connected to terminals L and M, furnishrespectively the anode and filament voltages for the full-wave rectifiertube 59. The extremities of the secondary winding of transformer 56 areconnected through the A. C. windings of saturating transformers 57, tothe anodes of tube 59 and to the ends of resistor 58. This resistorfurnishes an adequate load for the saturating transformers by drawing analternating current through the A. C. windings thereof. It is noted thatwithout this A. C. loading the saturating transformers 57 could notproperly control the A. C. input voltage to the rectifier,- since theywould be required to operate on the pulsating D. C. drawn by therectifier. The rectifier output voltage taken from the secondary windingcentertaps of transformers 56 and 60 is filtered by capacitor 61 andappears across resistor 62 and terminals B and G. The D. C. windings oftransformers 57 are connected in a series-opposing relationship so thatthe A. C. voltages induced therein by the A. C. windings will becancelled out. Capacitor 55 is connected across these seriate D. C.windings to furnish a low impedance path for any residual induced A. C.currents and to bypass any high frequency arc current variations thatmight affect the operation of the rectifier. Resistor 63 is also shuntedacross the seriate D. C. windings of transformers 57 and serves as anarc current control whereby the proportion of the total are cur-' rentflowing through these windings may be varied manually. In operation thecircuit furnishes a negative bias voltage to the calutron controlelectrode 35, the magnitude of which is varied by the saturatingtransformers 57, the impedance of these transformers in turn beingcontrolled by the arc current. For example, if the are current tends toincrease, the impedance presented by the A. C. windings of transformers57 decreases and the A. C. voltage delivered to the rectifier increases.The resulting increase in rectified output voltage provides an increasednegative bias on control electrode 35, reducing the bombardment currentto the bombardment cathode 47 and lowering its thermionic emission. Theconsequent decrease in arc current opposes the original tendency toincrease and thus stabilizes the arc current about a predeterminedvalue.

In Fig. 4 another modification 46b of the arc regulator is againassociated with the arc current by means of terminals J and K. In thiscase, however, the output voltage developed by the regulator isimpressed between the control electrode 35 and the bombardment cathode37, this being in effect equivalent to applying the voltage between thecontrol electrode 35 and the filamentary cathode 25, since filamentarycathode 25 is displaced electrically from bombardment cathode 37 by' thesubstantially constant potential of the bombardment'voltage supply 44-.Transformer 66, powered from a suitable source of alternating currentconnected to terminals L and M, furnishes the anode and filamentvoltages for the grid controlled rectifier tubes 67. The rectifiedoutput voltage from these tubes is filtered by the inductance 68 andcapacitors 69 and 70 and appears across resistor 71, the negativeterminal thereofbeing connected through terminal G to the ion generatorcontrol electrode 35 and the positive terminal thereof being connectedthrough potentiometer 73 and terminal I to thejbombardm'ent cathode 37of the ion generator. A D; C-. bias proportional to the arc currentisimpressed upon the grids of tubes 67 througlithevariable contactorofpotentiorneter 73 This potentiometer 73- is connectedin se rics withthe arc current circuit through terminals I and K and serves as the arccurrent control. It isob served that the potential drop produced by theare cur rent flowing through the resistor of potentiometer 73 adds tothe control voltage produced by the rectifier and thus assists in theregulating action. In operation, an increase in arc current biases thegrids of tubes 67 more positively and thus increases the output voltagefrom the rectifier. This biases the ion generator control electrode 35more negatively with respect to the filamentary cathode 25 and hencereduces the bombardment current to bombardment cathode 37. Again, theconsequent reduction in bombardment cathode emission causes a reductionin arc current which opposes the original increase. Stabilization of thearc current is thus attained. v In Fig. 5 still another modified form460 of arc regulator is illustrated. Transformer 75 and transformers 79,powered from a suitable alternating current source through terminals Land M, furnish anode, filament and voltages for the grid-controlledfull-wave rectifier tubes 78. The output voltage from this rectifier,appearing across resistor 77 and capacitor 76, is impressed between thecontrol electrode 35 and filamentary cathode 25 of the ion generator 20through terminals G and B which are connected respectively to thecontrol electrode 35 and the filamentary cathode 25. The A. C. windingsof the saturating transformers 80 are series-connected between theabove-mentioned source of alternating current and the paralleledprimaries of grid transformers 79 and consequently govern the magnitudeof the A. C. grid voltages impressed on tubes 78. The D. C. saturatingwindings of these transformers 80 are connected in seriesopposition intothe arc current circuit by means of terminals K and J. An adjustableportion of the are current is diverted from these windings by theshunt-connected resistor 81, which thereby serves as the arc currentcontrol. It is noted that in this arrangement the impedance of the A. C.windings of transformers 80 also influences to an appreciable extent thephase of the A. C. grid voltages supplied to tubes 78 and thus effects agreater degree of control than would otherwise be attainable' withmagnitude variation alone. In the operation of the circuit an increasein arc current decreases the impedance of transformers 80 and increasesthe voltage supplied to the primaries of the transformers 79. Theincreased positive grid voltages on tubes 78 during the conductinghalf-cycle results in an increased output voltage being impressed oncontrol electrode 35. This in turn reduces the bombardment current, thebombardment cathode emission, and the arc current. Thus a closedregulating loop again obtains whereby the are current is stabilized.

While there has been described what is at present considered to be thepreferred embodiments of the invention, it will be further understoodthat various modifications may be made therein and it is intended tocover in the appended claims all such modifications as fall within thetrue spirit and scope of the invention.

What is claimed is:

1. A regulator for an electric discharge device comprising incombination an electron-emissive cathode, a bom-' bardment cathode, acontrol electrode therebetween, meansfor maintaining said bombardmentcathode at a positive potential with respect to said electron-emissivecathode whereby said bombardment cathode is heated to emissivetemperature by electron bombardment, an anode, means for maintainingsaid anode at a positive potential with respect to said bombardmentcathode whereby an electric discharge is maintained therebetween, and avariable impedance device connected to said control electrode and havingan inductive control member connected in series with said electricdischarge and responsive to the current thereof, whereby the potentialof said coritrol eletr'ode is controlled in accordance with saiddischarge current. v

2'. A regulator for an electric discharge devicecoriiprising incombination an electron-emissive cathode, a bornbardment cathode, acontrol electrode therebetween',

means for maintaining said bombardment'cathode at apositive potentialwith respect to said electron-emissive cathode whereby said bombardmentcathode is heated to emissive temperature by electron bombardment, ananode, means for maintaining said anode at a positive potential withrespect to said bombardment cathode whereby an electric discharge ismaintained therebetween, and thermionic means having an inductivecontrol member responsive to said electric discharge current forcontrolling the potential of said control electrode.

3. A regulator for an ion generator of the arc discharge type comprisingin combination a filamentary cathode, means for heating said filamentarycathode to electronemissive temperature, a bombardment cathode, acontrol electrode intermediate said filamentary and bombardmentcathodes, means for maintaining said bombardment cathode at a positivepotential with respect to said filamentary cathode whereby saidbombardment cathode is heated to electron-emissive temperature byelectron bombardment, an anode, an arc supply for maintaining said anodeat a positive potential with respect to said bombardment cathode wherebyan arc discharge is obtained therebetween, and electronic meanscontrolled by said are discharge current for supplying a variablevoltage to said control electrode whereby said are current may beregulated by control of the bombardment current to said bombardmentcathode.

4. A regulator for an ion generator of the arc discharge type comprisingin combination a filamentary cathode, means for heating said filamentarycathode to electronemissive temperature, a bombardment cathode, acontrol electrode intermediate said filamentary and bombardmentcathodes, means for maintaining said bombardment cathode at a positivepotential with respect to said filamentary cathode whereby saidbombardment cathode is heated to electron-emissive temperature byelectron bombardment, an anode, an arc supply for maintaining said anodeat a positive potential with respect to said bombardment cathode wherebyan arc discharge is obtained therebetween, and variable impedanceelectronic means controlled by said are discharge current for supplyinga variable voltage to said control electrode whereby said are currentmay be regulated by control of the bombardment current to saidbombardment cathode.

5. A regulator for an ion generator of the arc discharge type comprisingin combination a filamentary cathode, a source of heating current forsaid filamentary cathode, a bombardment cathode, a bombardment voltagesupply for maintaining said bombardment cathode at a positive potentialwith respect to said filamentary cathode whereby said bombardmentcathode is heated to electron-emissive temperature by electronbombardment from said filamentary cathode, a control electrode disposedbetween said filamentary cathode and said bombardment cathode, an anode,an arc supply for maintaining said anode at a positive potential withrespect to said bombardment cathode whereby an arm discharge is obtainedtherebetween, an electromagnetic winding connected in series with saidare supply, a thermionic device associated with said electromagneticwinding, the impedance of said thermionic device being controlled by thearc current through said electromagnetic winding, and said controlelectrode whereby the arc current controls the potential of said controlelectrode with respect to said filamentary cathode to maintain said arccurrent substantially constant.

6. A regulator for an ion generator of the arc discharge type comprisingin combination a filamentary cathode, a source of heating current forsaid filamentary cathode, a bombardment cathode, a bombardment voltagesupply for maintaining said bombardment cathode at a positive potentialwith respect to said filamentary cathode whereby said bombardmentcathode is heated to electron-emissive temperature by electronbombardment from said filamentary cathode, a control electrode disposedbetween said filamentary cathode and said bombardment cathode, an

anode, an arc supply for maintaining said anode at a positive potentialwith respect to said bombardment cathode whereby an arc discharge isobtained therebetween, a magnetron having an electromagnetic windingconnected in series with said are supply and having a thermionic devicecontrolled by said electromagnetic winding, the im pedance of saidthermionic device being controlled by the arc current through saidelectromagnetic winding, and means connected between said thermionicdevice and said control electrode whereby the arc current controls thepotential of said control electrode with respect to said filamentarycathode to maintain said are current substantially constant.

7. A regulator for an ion generator of the are discharge type comprisingin combination a filamentary cathode, a source of heating current forsaid filamentary cathode, a bombardment cathode, a bombardment voltagesupply for maintaining said bombardment cathode at a positive potentialwith respect to said filamentary cathode whereby said bombardmentcathode is heated to electron-emissive temperature by electronbombardment from said filamentary cathode, a control electrode disposedbetween said filamentary cathode and said bombardment cathode, a biasrectifier for biasing said control electrode with respect to saidfilamentary cathode, an anode, an arc supply for maintaining said anodeat a positive potential with respect to said bombardment cathode wherebyan arc discharge is obtained therebetween, and a saturable reactorhaving a D. C. winding and A. C. windings, said D. C. winding beingconnected in series with the arc supply and said A. C. windings beingconnected to control the input power to said bias rectifier whereby thepotential of said control electrode is controlled by the arc current tomaintain the arc current of said ion generator substantially constant.

8. A regulator for an ion generator of the arc discharge type comprisingin combination a filamentary cathode, a source of heating current forsaid filamentary cathode, a bombardment cathode, a bombardment voltagesupply for maintaining said bombardment cathode at a positive potentialwith respect to said filamentary cathode whereby said bombardmentcathode is heated to electron-emissive temperature by electronbombardment from said filamentary cathode, a control electrode disposedbetween said filamentary cathode and said bombardment cathode, means forbiasing said control electrode with respect to said filamentary cathode,an anode, an arc supply for maintaining said anode at a positivepotential with respect to said bombardment cathode whereby an arcdischarge is obtained therebetween, and a saturable reactor having a D.C. winding and A. C. windings, said D. C. winding being connected inseries with the arc supply and said A. C. windings being connected tocontrol the input power to said control electrode bias means whereby thepotential of said control electrode is controlled by the arc current tomaintain the arc current of said ion generator substantially constant.

9. A regulator for an ion generator of the arc discharge type comprisingin combination a filamentary cathode, a source of heating current forsaid filamentary cathode, a bombardment cathode, a bombardment voltagesupply for maintaining said bombardment cathode at a positive potentialwith respect to said filamentary cathode whereby said bombardmentcathode is heated to electron-emissive temperature by electronbombardment from said filamentary cathode, a control electrode disposedbetween said filamentary cathode and said bombardment cathode, an arcanode, an arc supply for maintaining said are anode at a positivepotential with respect to said bombardment cathode whereby an arcdischarge is obtained therebetween, a resistor connected in series withsaid are supply, and a bias supply for said control electrode having agrid controlled thermionic rectifier, the grid circuit of saidthermionic rectifier being connected to said resis' tor whereby thecontrol electrode bias is controlled by arse-me the are current tostabilize the are Current of saidion generator at a substantiallyconstant value.

10. A regulator for an ion generator of the are dis charge typ'ecomprising in combination a filamentary cathode, a source of heatingcurrent for said filamentary cathode, a bombardment voltage supply formaintaining said bombardment cathode at a positive potential withrespect to said filamentary cathode whereby said bornbardment cathode isheated to electron-emissive temperature by electron bombardment fromsaid filamentary cathode, a control electrode disposed between saidfilamentar'y cathode and said bombardment cathode, an arc anode, an arcsupply for maintaining said are anode at a positive potential withrespect to said bombardment" cathode whereby an' arc discharge isobtained therebetwee'n, a bias supply for said control electrode, saidbias supply having grid co'r'itrolled thermionic rectifying devices,transformers for supplying A. C. grid potentials to said thermionicrectifying devices, and a saturable reactor having a D. C. and an A. C.winding, said A. C. winding being connected in series with the powerline feeding said transformers, and said D. C.- winding being connectedin series with said are supply whereby said control electrode potentialis controlled by the arc current to maintainsaid arc currentsubstantially constant.

11. An electric discharge device comprising a first cathode, a secondcathode, a control g'riddisposed between said first cathode and saidsecond cathode, an anode, means for rendering said first cathodeelectronemissive, means for applying a negative potential to said firstcathode With respect to said second cathode whereby electrons emitted bysaid first cathode bombard said second cathode in order to raise saidsecond cathode to thermionic emission, means for applying a'positivepoten tial to said anode with respect to said second cathode whereby anelectric discharge is established betweeen said second cathode and saidanode, and means responsive to variations of said electric dischargecurrent for applying a bias potential to said control grid. 7

12. An electric discharge device comprising a first cathode, a secondcathode, a control grid disposed between said first cathode and saidsecond cathode, an anode, means for rendering said first cathodeelectronemissive', means for applying a negative potential to said firstcathode with respect to said second cathode whereby electrons emitted bysaid first cathode bombard said s'e'c-" end cathode in order to raisesaid second cathode to thermionic emission, means for applying apositive potential to said anode with respect to said second cathodewhereby an electric discharge is established between said second cathodeand said anode, and amplifying means including a vacuum tube responsiveto variations of said electric discharge current for applying a bias'potential to said control grid.

References Cited in the file of this patent UNITED STATES PATENTS1,309,704 Stoekle July 15, 1919 1,419,547 Ehret June 13, 1922 1,628,678Morrison May 17, 192'! 2,149,080 Wolff Feb. 28, 1939, 2,408,091 OlesenSept. 24, 1946

1. A REGULATOR FOR AN ELECTRIC DISCHARGE DEVICE COMPRISING INCOMBINATION AN ELECTRON-EMISSIVE CATHODE, A BOMBARDMENT CATHODE, ACONTROL ELECTRODE THEREBETWEEN, MEANS FOR MAINTAINING SAID BOMBARDMENTCATHODE AT A POSITIVE POTENTIAL WITH RESPECT TO SAID ELECTRON-EMISSIVECATHODE WHEREBY SAID BOMBARDMENT CATHODE IS HEATED TO EMISSIVETEMPERATURE BY ELECTRON BOMBARDMENT, AN ANODE, MEANS FOR MAINTAININGSAID ANODE AT A POSITIVE POTENTIAL WITH RESPECT TO SAID BOMBARDMENTCATHODE WHEREBY AN ELECTRIC DISCHARGED IS MAINTAINED THEREBETWEEN, AND AVARIABLE IMPEDANCE DEVICE CONNECTED TO SAID CONTROL ELECTRODE AND HAVINGAN INDUCTIVE CONTROL MEMBER CONNECTED IN SERIES WITH SAID ELECTRICDISCHARGE AND RESPONSIVE TO THE CURRENT THEREOF, WHEREBY THE POTENTIALOF SAID CONTROL ELECTRODE IS CONTROLLED IN ACCORDANCE WITH SAIDDISCHARGE CURRENT.